Last December, Democrat Doug Jones won a Senate race in Alabama by defeating a horribly flawed Republican candidate Roy Moore. For the first time, it appeared that the Democrats had a plausible path to winning control of the U.S. Senate in 2018. The Republican advantage was trimmed to a 51-49 margin and a net change of two seats would make New York Senator Chuck Schumer the new Senate Majority leader.

To win the Senate, all the Democrats had to do was win GOP seats in Arizona and Nevada and successfully defend all of their incumbents. At the time, the Democrats had a double-digit lead on the Generic Congressional Ballot and being opposed to President Trump seemed to be all that was needed. It looked like the Democrats were poised to ride a blue wave back to power.

My, how times have changed!

Shortly after Doug Jones won that special election in Alabama, the Republicans in Congress cut taxes and eliminated the Obamacare mandate. Having demonstrated that they could do something that their voters wanted, the GOP prospects began to improve. Now, with the elections just six months away, it seems that Republican are more likely to gain seats in the Senate rather than lose control.

Sure, it's still possible that the Dems could pick up seats in Arizona and Nevada. But, such an outcome is far from a sure thing as both races are now toss-ups.

And, even if Schumer's party wins both of those races, the chances of successfully defending all of the vulnerable Democratic incumbents is increasingly in doubt. The Dems are playing defense hoping to hang on to five Senate seats in states that President Trump won by double digits -- West Virginia, Indiana, Missouri, North Dakota, and Montana. On top of that, Florida Governor Rick Scott has entered the fray to challenge Democratic Senator Bill Nelson in a toss-up state. Early indications are that Scott has all the energy and momentum in the race.

The numbers clearly favor the GOP. If, for example, the Democrats pick up BOTH toss-up races in Arizona and Nevada, the Republicans need to win just one of the other six competitive races to keep the Senate at a 50-50 tie. With Vice President Mike Pence empowered to cast the deciding vote, the GOP would remain in control.

At this moment in time, however, it seems like the Republicans should expect to do much better than a mere 50-50 tie in the Senate. There is certainly a chance they could win at least one of the toss-up Senate races in either Arizona or Nevada (especially if Martha McSally wins the Republican nomination in Arizona).

Beyond that, Democrats Claire McCaskill and Joe Donnelly face uphill battles in Missouri and Indiana. It's very easy to imagine the R's picking up at least one of those seats. Democrat Heidi Heitkamp is probably a slight underdog in her North Dakota re-election bid. In West Virginia, Joe Manchin's personal popularity may be enough to overcome the fact that President Trump carried the state by 42 points -- but it will probably be very close. And, as always, Florida remains a pure toss-up.

Add it all up, and the Democrats need to pull an inside straight to avoid losing seats in the Senate this November.